Wading into the government’s use of the state secrets privilege to ward off lawsuits, a sharply divided federal appeals court on Wednesday tossed a legal challenge to the CIA’s so-called “torture flights,” concluding that allowing the case to proceed against a San Jose-based company could expose critical national security secrets.

In siding with the Obama administration’s privilege arguments, the 9th U.S. Circuit Court of Appeals ruled that a lawsuit could not proceed that alleges five former terrorism suspects were transported to foreign countries and subjected to brutal CIA interrogation tactics. The lawsuit was filed against Jeppesen Dataplan, a Boeing subsidiary accused of carrying out the flights under a contract with the government.

The Obama administration moved to dismiss the lawsuit, invoking the same state secrets argument embraced previously by the Bush administration. The 9th Circuit, in a 6-5 ruling, sided with the government, setting up a possible chance for the U.S. Supreme Court to take a fresh look at the circumstances under which White House officials can insulate government conduct against legal attacks.

“Further litigation presents an unacceptable risk of disclosure of state secrets no matter what the legal or factual theories Jeppesen would choose to advance during a defense,” 9th Circuit Judge Raymond Fisher wrote for the majority. “Whether or not Jeppesen provided logistical support in connection with the extraordinary rendition and interrogation programs, there is precious little Jeppesen could say about its relevant conduct and knowledge without revealing information about how the United States government does or does not conduct covert operations.”

Michael Pound, a Jeppesen spokesman, declined to comment. Jeppesen and Boeing have refused to discuss the company’s relationship with the CIA, or the allegations raised by the five detainees who say they were tortured after the Sept. 11, 2001, terror attacks.

In a dissent, Judge Michael Daly Hawkins said the privilege was being applied too broadly and too soon in the litigation.

The five dissenters argued that the case should proceed to determine if Jeppesen could defend its conduct without “resorting to state secrets evidence.”

The lawsuit was filed in 2007, but was quickly immersed in the privilege issue. U.S. District Judge James Ware sided with the Justice Department and dismissed the case on state secrets grounds, but a three-judge 9th Circuit panel reinstated the lawsuit two years later, rejecting the government’s argument.

The 9th Circuit then agreed to rehear the case with an 11-judge panel. The American Civil Liberties Union, which brought the legal challenge to the extraordinary rendition program, vowed to appeal the ruling to the U.S. Supreme Court.

“If today’s decision is allowed to stand, the United States will have closed its courtroom doors to torture victims while providing complete immunity to their torturers,” said Ben Wizner, an ACLU staff attorney.

Among other things, ACLU lawyers have insisted that most of the evidence of the rendition program and Jeppesen’s role in participating is already public, negating the government’s right to assert the material is secret. This includes alleged evidence from a former Jeppesen employee who asserted that the Boeing subsidiary carried out the flights for the CIA.

But the 9th Circuit majority disagreed, saying the judges had reviewed the classified material and came away “convinced that at least some of the matters (the government) seeks to protect from disclosure in this litigation are valid state secrets.”